Long QT Syndrome (LQTS)

Etiology- 
- Once considered rare
- now found to just be concealed by other diagnosis
- Causes
		Drugs
		- antianginals
		- Antiarrhythmics
			-Class Ia 
			- Class III
		- Antibiotics ( Erythro, Pentamidine, Tmp/sulfa)
		-Antifungals (Fluconazole, itraconizole, Ketoconazole)
		- Antihistamines (Astermizole, Terfenadine)
		- Antipsychotics (Haloperidol, Respiridone, Phenothiazines)
		- Lipid lowering drugs (Probucol)
		- Oral Hypoglycemic (glibeclamide, Gliburide)
		- Organophosphates
		- Promotil agent (Cissapride)

	Electric disturbances
		- Acute hypokalemia (Associated with Diuretics & hyperventilation)
		- Chronic hypocalcemia
		- Chronic Hypokalemia
		- Chronic hypomag

	Underlying Medical Disorders
		- Arrhythmia ( Complete AV block, bradycardia, sick sinus)
		- Cardiac ( Anthracycline tox, CHF, myocarditis, tumors
		- Endocrine (hyperpararthyriod, Anorexia Nervosa, starvation, liquid 
protein diet)

PERTINENT FAMILY HISTORY

	-Unexplained fatal accidents (ie single auto accidents)
	- SIDS
	- Familial epilepsy or fainting spells

SYNDROMES -

	- Jewell & Lange-Nielsen
		- rare 1to 6/miliion
		- Autosomal Recessive
		- Sensorial Hearing loss
	- Romano Ward
		- Not Rare just underdiagnosed
		- Heterogeneous collection of 6 genotypes
		- 1 in 10,000
		- No Gender
		- Accounts for 4,000 SIDS /yr

PRESENTATION

-Can strike quickly, 1/3 of previously healthy kids die suddenly

- 60 % have activity or emotion-related syndromes
	- Syncope
	- Sz
	- Palpitations
	if sx related to fight or flight LQTS should be concidered
	Swimming seems to be a particular trigger

	Often misdiagnosed as epilepsy
		Cerebral Ischemia 2° to ventricular arrhythmia
		-sequence- Dizziness, lightheadedness, blackout, LOC, then sz.

More than 1/3 are asymptotic 

EVALUATION

	EKG
	Determine QTc ( QT/sq rt R-R)
	inspect T waves

TREATMENT

10 yr mortality is 50 % w/therapy 	<5%

ß- blockers
Pacemakers/Defibrilators
Left cervicothoracic sympathetic ganglionectomy

Role of 1° care physician is to:
	monitor compliance
	watch for side effects
		Depression 
		bronchospasm
	Facilitate tx w/ breakthroughs

Some experts recommend tx every one with LQTS because 1/3 present DOA
Always treat if QT > .6
No competitive sports, and always with a buddy

Tx for electrolyte imbalance is Mg

    Source: geocities.com/southbeach/pointe/5375/Dailybread/Medical

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